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Of HVAC Drains and Clogging

So the other day my upstairs thermostat went blank on me. The downstairs thermostat died in similar fashion last year and I had to replace it, so I assumed that they were shoddy devices the builder had installed with a 3ish year half-life, so went ahead and bought a fancy new one to replace it with. Only to discover that the problem wasn't the thermostat, it was that there wasn't any powering coming down the hot wire from the HVAC transformer.

Investigation in my attic revealed that the backup drainage catch pan under the heater was full of water, which had tripped the sensor device designed to cut the system off in the event that said pan fills up with water (prior to water washing over the edge and coming down through my ceiling, so yay for that). Presumably there is a blockage in the drainage pipe leading out of the house from the unit. Conveniently the builder installed a u-bend and a hand-tight cap. Inconveniently, the cap is on the outside of the u-bend and above the turn where the pipe leads out of the house. I don't really want to chop up and re-splice the PVC, so I'm curious what the best way to go about clearing this thing out is. I figure I can just use a bent coat hanger to fish out the u-bend in case the clog is there, but I'm a bit stumped on the long run out to the side of the house.

I considered buying a plumbing snake, but I'm not sure how I'd get it into around the corner to head out of the house.

I have a fairly beefy wet/dry vac (I used it to get the water out of the catch pan, in fact, to make sure that the unit came back on once that issue was cleared up). Would it be a good idea to duct tape the end of the hose to one end of the drain pipe and fire it up? It's 1" PVC and probably... I don't know... between 50 and 100 feet from the heater to the open drain outside the house. If this isn't a terrible idea, should I hook up the vac to the heater end, or to the outside the house end?

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There was no hand-tightened cap for me to clean the trap, which was glued in place. Best of all, it was pouring into an open drain, so the trap wasn't even really necessary. As a result, the drip tray started to fill up, and guess what...it's lower than the drain it's hooked up to, so it never drained. Being in a tiny condo with no wet/dry vac, I had to get all that water out by hand.

My solution was to just cut apart the PVC and run a straight, slightly-downward sloped 1" PVC pipe to the drain bit. If your outbound pipe is sealed though, then you might actually need your trap. Having seen some of the more professional jobs in my unit, by actual HVAC guys, I can tell that they use neat little clear traps with flip-up lids that make for easy cleaning (there's even a clip for the pipe cleaner brush!)

That being said, I found nothing of the sort at any of Home Depot/Lowes/etc. I was told to go to an actual plumbing store (wherever the fuck I might find one of those...) and they might have one. The problem is that no matter what you do, that trap is going to clog up again, so you need to find a solution that you'll actually be able to clean. Does your water heater have any ingress into the trap?

It's actually my central heater, not my water heater. But no, I don't see a way to get into it from the heater end. At least not without disassembling the unit, which I'm unwilling to do. It's gas heat and while poking things with a multimeter and cleaning out condensation drain pipes are within my realm of comfort, anything that involves removing panels with warning labels on them behind which is a system that processes explosive gas is not something I'm going to mess with.

There's a glued-on cap above the heater-side of the u-bend. Maybe I'll cut it off and put my own cap on. Hopefully the clog is, in fact, in the bend and not somewhere 30 feet down the pipe on its way out of the house. I saw a dude on the internet who said he put bleach down his drain pipe to clear out algae buildup, but I'm not sure how I could do that with the current setup. You'd think "how to hook up a condensation drain pipe to ensure easy access for cleaning" would be a solved problem at this point. There shouldn't be variartions. Unless the guy who did mine was just stupid and put it together backwards or something.

Seems like if you had a wet/dry vac you could attach it to the end of the pipe that exits the house and slurp it all out. Supposedly you can just cut the PVC pipe right in front of the furnace assuming you leave enough pipe that you can add a connector later.

Warning: I am a programmer/sysop. Do not take my word as law in any other fields, it is not professional advice.

It's actually my central heater, not my water heater. But no, I don't see a way to get into it from the heater end. At least not without disassembling the unit, which I'm unwilling to do. It's gas heat and while poking things with a multimeter and cleaning out condensation drain pipes are within my realm of comfort, anything that involves removing panels with warning labels on them behind which is a system that processes explosive gas is not something I'm going to mess with.

There's a glued-on cap above the heater-side of the u-bend. Maybe I'll cut it off and put my own cap on. Hopefully the clog is, in fact, in the bend and not somewhere 30 feet down the pipe on its way out of the house. I saw a dude on the internet who said he put bleach down his drain pipe to clear out algae buildup, but I'm not sure how I could do that with the current setup. You'd think "how to hook up a condensation drain pipe to ensure easy access for cleaning" would be a solved problem at this point. There shouldn't be variartions. Unless the guy who did mine was just stupid and put it together backwards or something.

Yeah sorry, I meant central heater.

I'd just cut the cap off and put your own on there, then throw a pipe snake or whatever in there to try and loosen some junk up. That would also afford you the opportunity to pour bleach or whatever in there, although I don't know how well bleach/draino/etc plays with PVC.